Predation on early ontogenetic life stages and its effect on recruitment into a marine epifaunal community

In a New England (USA) subtidal hard-substrate community, 2 species of very small gastropods, Anachis lafresnayi and Mitrella lunata, prey on several species of newly settled ascidians. Preliminary expenments indicated that this predation drastically changes ascidian recruitment patterns. In order to examine this phenomenon more fully, an extensive series of field expenments using artificial substrates was performed over a 2 yr period between 1991 and 1992. In 1992, weekly experiments were conducted over the complete recruitment season between July and October. Comparisons of the experiments were made to test for any weekly or annual variation m the effect of these micro-predators on recruitment. Results demonstrated that the predators (1) were fairly specific in their prey preferences, (2) could eliminate prey species regardless of their settlement density, (3) switched prey in response to changes in prey species abundance, and (4) affected recruitment throughout the entire settlement season. These results indicate that processes affecting post-settlement life stages contribute significantly to the overall dynamics of communities and must be considered along with the much better documented effects of larval supply, adult predators, and physical disturbance.